Disposable cups have long been known. For many years such cups were made of paper treated with wax or the like. Such cups have seams which are prone to leak, and also provide an undesirable taste of their own. Accordingly, seamless plastic cups have come into widespread use, particularly in vending machines. Such cups are typically produced by a plug-assisted blow molding process of a thermoplastic material, polystyrene being one preferred example. Pioneering and commercially successful such cups are shown in my own prior U.S. Pat. Nos. 3,091,360 and 3,319,213, for example. The cups in the two patents just noted are provided with stepped sidewall portions providing relatively inefficient heat transfer from the cup contents to the fingers of a user. However, there are instances in which the cup contents may be so hot that it is not very comfortable to hold such in the fingers for an extended period of time.
For some types of comestibles automatically vended in plastic cups it is a simple matter to provide two or more sources of liquid to provide desired flavors, etc., soft drinks being a common example. In other instances it is desired to use a dried powder or the like, such as for coffee, hot chocolate, chicken soup, etc. Powders are not so readily handled in vending machines. Accordingly, it has heretofore been proposed to provide a stack of plastic cups in which a food concentrate or the like is stored in the bottom of each cup, the next above adjacent cup providing a seal to protect the food concentrate, see U.S. Pat. No. 3,512,677. It also is known to provide cups with a double-spaced wall construction providing an air space for insulation, see for example U.S. patent application Ser. No. 340,122, filed Mar. 12, 1973 by Robert H. Day. The present invention relates to a cup specifically of the last mentioned type.